1. Field of the Invention
This invention relates to ink jet printing, and more particularly, to ink compositions for ink jet printers
2. Description of Related Art
Ink compositions, especially those for use with ink jet printers, must satisfy a number of conditions in order to achieve acceptable printing.
The ink composition should possess properties which permit it to be jetted appropriately from an ink jet printer. In ink jet printing, droplets of ink are expelled from nozzles onto a recording medium. The ink should form a meniscus at each nozzle prior to being expelled in the form of a droplet. After a droplet is expelled, additional ink surges to the nozzle to reform the meniscus. Important properties of the ink in this context include the ink's viscosity and surface tension.
Further, in many applications, fast drying inks are desired. However, the drying time of the ink should not be such that it dries in the nozzle of the ink jet printer, thus clogging the nozzle. On the other hand, slow drying inks have limited use in printers requiring high throughput.
Generally, adjustment of the viscosity of an ink composition can negatively affect the print quality and/or drying time of the ink. This may result in excessive feathering or wicking along the paper fibers due to capillary action and longer drying times, which can result in variations in the boundary of characters or edge raggedness. Adjustments to the surface tension to improve a certain characteristic of the ink may adversely affect other characteristics thereof.
Other desirable properties for ink jet ink compositions include good water fastness and latency. Latency is the maximum time period, usually less than one hour and most often less than 10 minutes, over which an uncapped ink jet printhead can remain idle before noticeable deterioration of its jetting performance occurs.
A number of ink compositions for ink jet printing have been proposed.
U.S. Pat. No. 4,508,570 to Fujii et al. discloses an aqueous ink comprising a water-soluble dye; a polyhydric alcohol and/or an alkyl ether; water; and at least one water-soluble non-ionic surface active agent. The non-ionic surface active agent may comprise a polyoxyethylene alkyl amine, polyoxyethylene alkyl phenyl ether, and polyoxyethylene alkyl ether. The disclosed polyoxyethylene alkyl amine is a tertiary amine.
U.S. Pat. No. 4,923,515 to Koike et al. discloses a recording liquid composition comprising water, an organic solvent, and a water-soluble dye. The organic solvent may include block copolymers of ethylene oxide and propylene oxide.
U.S. Pat. No. 4,853,036 to Koike et al. discloses an ink composition comprising a liquid composition, a volatile solvent, and solid material. The solid material may comprise polyethylene glycol, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and polyoxyethylene/polyoxypropylene block copolymers.
Although the ink compositions of the prior art provide inks with certain advantageous qualities, it is desirable to provide inks having good print quality in which the drying times may be adjusted while also maintaining good water fastness and latency.